1. Field of the Invention
The present invention relates generally to an improved ultra-wide band micro-power impulse radar sensor, for detecting motion or other characteristics of objects within a range gated field.
2. Description of Related Art
Prior art motion sensors have been primarily based on ultra sound, passive infrared sensors, and so-called FM-CW radar sensors. Also, some Doppler radar systems have been used for motion detection in prior art. All of these prior art systems suffer a number of limitations that make them impractical for a large number of uses.
As described in U.S. Pat. No. 5,361,070, of which the present application is a continuation-in-part, an ultra-wide band radar motion sensor overcomes many of the disadvantages of these prior art systems.
However, radars that employ extremely wide RF bandwidths generally use wide band oscilloscopes or sampling circuits as direct conversion receivers since the use of intermediate frequencies (IF) is precluded by the large bandwidths involved. For instance, receivers for the wide band radar motion sensors have been based on amplification at base band or close to DC, resulting in high noise levels due to the 1/f noise in virtually all electronic devices. Also, high gain at a single frequency frequently leads to oscillations due to input/output signal feedback. Additional problems include: 1) problems with jamming signals, which are indistinguishable from authentic radar returns and may result in false alarms; 2) high level impulse noise sources weigh heavily on the averaging process in the receiver, because such impulses cannot be easily clipped in amplitude; 3) the receiver relies on simple Gaussian averaging for selectivity and for rejection of interference, which can lead to false triggering at high jamming levels; 4) there is no received "carrier" to operate an automatic gain control circuit for more consistent performance and wider dynamic range; 5) there is no means to encode transmissions for selective reception in co-located systems; 6) and there is no way to deduce the direction of movement, or to deconvolve the pseudo-Doppler returns in the magnitude and phase components for signal processing. Accordingly, it is desirable to improve the wide band radar motion sensor to address the issues related above.